The present invention relates to machines for tamping railroad track, particularly in switches.
When tamping tangent track, where the spacing of the individual rails of the track is constant, it is necessary only to provide for the up and down movement on the tamping machine of the tamping units into and out of the ballast to be tamped. However, on entering a switch, where two tracks merge the spacing between the rails of the tracks varies and this requires the provision of some means to transversely alter the position of the tamping units relative to the tamping machine frame to accommodate the rail spacing changes.
There have been different solutions proposed to the problem of tamping in switches.
One common solution is the use of pendulum type workheads. Canadian Pat. No. 938,498 is an example of this type of workhead. Here a machine has four independently manoeuvrable tamping workheads pendulously mounted for movement transversely of the track to be tamped. This solution gives a very complete tamping pattern but suffers from one fundamental drawback in that as the workheads are swung, the depth of penetration of the tamping tools in relation to the bottom of the ties to be tamped changes, resulting in non-uniform ballast compaction. This deficiency can be compensated but only with considerable expense and the use of complex technology.
A proposal has been made to overcome the tamping depth problem encountered by the pendulum type of switch tamping machine and in this solution tamping heads are mounted so as to be able to be transversed laterally horizontally of the track on a guide frame. This solution has utilised a conventional tamping head such as that described in U.S. Pat. No. 3,426,697 and whilst this solution overcomes the tamping dept problem, it results in a machine which requires more time to negotiate the switch because the workheads require to be transversed at greater distances than the pendulum type and when the heads are transversed outward completely, as in the frog and switch point areas, they cause some disturbance to the shoulder ballast. Further on rail systems with electrified third rail it is not normally possible to tamp on the outside of the running rails in the areas of the frog and switch point.
Yet another proposal has been made, such as is shown in U.S. Pat. No. 4,576,095 in which again two workheads transverse laterally horizontally of the tamping machine. In this device the two tamping units which make up each of the two workheads have independent vertical movement. This has the advantage that the problem of shoulder ballast disturbance can be reduced or obviated. However this proposal suffers from the drawback that when a wide section of track structure is encountered, a complete tamping pattern is possible only with time consuming traversing of the workheads and frequent operation of the individual tamping unit vertical actuators.
According to the present invention there is provided a railroad switch tamping machine comprising a wheeled rail travelling vehicle; guide frame means extending transversely of the vehicle; four tamping units mounted for horizontal movement in translation and vertical displacement on the guide frame means; means for individually raising and lowering each of the four tamping units relative to each other tamping unit; and means for individually moving each of the four tamping units transversely on the guide frame means relative to each other tamping unit.
The present invention has the advantage that it can achieve a complete tamping pattern rapidly and with more ease than has been heretofore possible, and without paying the price of the tamping depth problem of the pendulum type tamping head, solution. The present solution also has the advantage that when doing out of face tamping the tamping units may be spread the optimum amount to accommodate such variables as rail width and length of bolts at joint bars, etc.
According to one feature of the present invention each tamping unit is mounted on its own sub-frame, each sub- frame engaging the guide frame means to mount its associates tamping head thereon, the means for individually transversely moving the tamping units comprising individual power units connected between each sub-frame and the guide frame means.
Preferably, the means for individually raising and lowering the tamping units comprises an individual power unit connected between each tamping unit and its sub-frame to vertically move the tamping unit in its sub-frame.
According to a preferred aspect of the invention there is provided a self propelled railroad switch tamping machine comprising a wheeled rail travelling machine; guide frame means extending transversely of the vehicle and including upper and lower longitudinally and vertically spaced guideways; four individual sub- frames mounted on the guide frame means for horizontal displacement in translation thereon and engaging the upper and lower guideways; individual power means connected between each sub-frame and the guide frame means for individually moving each sub-frame on said guide frame means transversely of the vehicle and relative to each other sub-frame; a tamping unit mounted for vertical movement in each sub-frame, and individual power means connected between each tamping unit and its associated sub-frame to vertically move each tamping unit in its sub-frame relative to each other tamping unit.